- Near-infrared spectroscopy (NIRS) is a functional imaging technique that can be uses light to study brain function while allowing for movement. To look at blood flow in the brain, NIRS uses a low-power light source with detectors that see how the light changes as it passes through brain tissue. Brain blood flow can indicate which parts of the brain are active during different tasks. Researchers want to study children with attention deficit hyperactivity disorder (ADHD) and autism spectrum disorders (ASD) and will use NIRS to compare the blood flow in the brain of children with ADHD and ASD with that of typically developing children.